Diabetes affects greater than 8.5% of adults globally, representing 422 million adults worldwide. This number is projected to increase to 642 million diagnosed adults worldwide by 2040 and, considering estimates that 45.8% of diabetes cases are undiagnosed, the number affected by 2040 may be over one billion. Onset of diabetes mellitus (DM) may affect a person's ability to drive a vehicle. In particular, hypoglycemia (low glucose level) is a key factor affecting the ability to drive, particularly in insulin-dependent DM because it leads to higher levels of blood pressure, sleep apnea, etc. While insulin is essential for survival in many patients with DM, close control over hyperglycemia (high glucose level), which reduces long-term complications of diabetes (retinopathy, neuropathy, renal disease, and cerebrovascular disease), can increase the risk of hypoglycemia.
Hypoglycemia and patterns of poor glucose control can impair the cognitive abilities (attention, memory, and decision-making) needed for performing complex tasks such as vehicle driving. When the glucose level falls below a certain threshold, these impairments can reduce driver performance. Cognitive impairments from hypoglycemia (particularly attention and executive dysfunction) can persist for hours after glucose levels return to normal. In drivers with DM, these impairments include self-awareness of internal physiological state. Self-awareness of internal physiological state (an executive function) may affect a driver's ability to mitigate risk. In normal functioning, the body releases epinephrine in response to hypoglycemia, producing autonomic effects that include increased heart rate. These autonomic effects provide internal cues to a driver with DM that he or she is impaired. Drivers affected with DM may be unable to recognize their hypoglycemic status and mitigate risk appropriately.